In the oil and gas industry, it is common to measure the volume and rate of flow of a fluid through a pipeline. The need for an accurate measurement is particularly acute in custody transfer applications, where custody of the fluid in the pipeline passes from a first owner to a second owner, and payment for the fluid may travel in the opposite direction.
A variety of meters are employed to measure the flow through a pipeline. One known type of meter is a positive displacement (PD) meter. FIG. 1A shows the general construction for the top works of a PD meter 100. The bottom 110 of a PD meter housing is suitable to attach to the internals of the PD meter by, e.g., screws or bolts. The internals of the PD meter is inserted into the pipeline to intercept the fluid flow. Fluid from the pipeline is forced to flow through a PD meter tube and causes a shaft protruding from the top works of the PD meter to spin, with one revolution of the shaft corresponding to a predetermined volume of fluid flowing through the PD meter. The volumetric flow of the fluid may be determined from the number of revolutions of the rotating components of the flow meter. Examples of the more common PD meters are oscillating piston, nutating disc, oval gear, roots, vane, rotor, and multi-piston.
Conventional PD meters attach to an electric pulser through a mechanical linkage. As shown in FIG. 1B, a mating coupling may include an offset pair of pins with a short extension attached to the shaft protruding from the PD meter. A shaft from the electric pulser includes an extension that fits between the offset pair of pins. During installation of the electric pulser, its shaft is positioned above the PD meter coupling by a technician, requiring alignment of shafts on the electric pulser between the pair of pins on the coupling. The electric pulser is then fastened to the PD meter during installation by a blind mating. Because this is merely a blind mating, even an experienced technician may take ten to fifteen minutes to align and fasten the components properly. In addition, because this is a mechanical linkage, over time wear occurs leading to slippage.